1. Field of the Invention
This invention relates to a technique for controlling the optical properties of material surfaces. More particularly, the present invention relates to a method for recording information by permanently altering the reflectivity of a surface with the application of heat by means of a high intensity light beam.
2. Discussion of the Prior Art
Heretofore, it is known to form optically recording media comprising a recording material upon selected portions of which a light signal having a high energy density is incident. The optical signal may be generated by a laser beam or an electron beam. The recording material may comprise a metal, such as bismuth, a dye or a resin which is thermally deformed, that is, melted or evaporated by thermal energy generated by exposure to the light signal. For example, it is known to record a laser beam or an electron beam whose amplitude has been modulated by an electric signal on a recording material which is thermally deformable. See, for example, U.S. Pat. Nos. 3,262,122 and 3,266,393 and Image Technology, pp. 31-35 (April/May 1970). It is also known to use a recording layer whose phase can be changed (see, e.g., U.S. Pat. No. 3,868,651) or which can be perforated (see, e.g., U.S. Pat. No. 4,000,334) or in which bubbles can be produced (see, e.g., U.S. Pat. No. 3,636,526). Such recording methods have the advantage of rapid processing and low cost and require no post-treatment. However, they also have low sensitivity or are degraded by many read cycles or are complicated to produce. This situation can be partially ameliorated by use of a porous substrate which has a lower thermal conductivity than a solid support; see, e.g., U.S. Pat. No. 4,032,691. Roughened surfaces have also been employed; see, e.g., Japanese Kokai 52-143838.